Macintosh System 1 - while not the first operating system that used a Graphical User Interface, it was the most successful. The OS used a desktop metaphor that included folders, and a trash barrel.

Unlike later versions, you could not “create” a new folder but rather rename “Empty Folder” found in the system folder. After renaming it, a new “Empty Folder” would appear. Also the Trash Can also worked differently, it would automatically delete all of its contents after each reboot.

Another new feature, that was as radical the GUI interface, no longer were you limited to keeping file names 8 bytes with a 3 byte extension. You could now name files and folder using names that made sense.

While graphical in nature System 1 was not multi-tasking, in other words, you could only run one program at a time.

Also the Macintosh File System or MFS was not hierarchical, in fact all files were stored at the root level but meta data like file location was stored in what was known as a resource fork. This information allowed the OS to visually sow files in folder while the were in fact physically stored at the root level. This being the case, there was no ability to nest folders within folders.